The proposed research is to develop an understanding of the imaging properties of time-modulated coded apertures as applied to nuclear medicine. Various codes and aperture geometries will be characterized according to their resolution and signal-to-noise properties. Iterative image reconstruction methods will be studied for obtaining longitudinal tomograms free of out-of-focus data and for absorption corrections. Using this information, optimal apertures will be constructed and evaluated for imaging specific organs, namely; the heart, thyroid, kidneys, and adrenals. Algorithms and specialized computer hardware will be developed and evaluated for very high speed 3-dimensional reconstruction of coded aperture images.